Inspecting wafers and photomasks (collectively, specimens) for defects and other characteristics is important for managing the semiconductor manufacturing process. Since the overall semiconductor manufacturing process involves hundreds of steps, it is critical to detect defects on the wafer or photomask early in the manufacturing process. To help detect defects that occur during the manufacturing process (as well as other specimen characteristics), manufacturers often employ automatic microscopic inspection systems.
Current microscopic inspection systems used by manufacturers are dedicated to either analyzing wafers for defects or analyzing photomasks for defects. Since wafers and photomasks have different dimensions and properties, separate microscopic inspection systems are used to accommodate these different dimensions and properties. For example, a stage included in an inspection system has a chuck attached to it that is specifically sized to hold either a wafer or photomask. Since a photomask is thicker than a wafer, existing chucks cannot be used for both photomasks and wafers. Unfortunately, buying and maintaining separate microscopic inspection systems can be very costly.
In a current wafer inspection system, in order to inspect both a wafer and a photomask using the same system, at the very least, a chuck that holds a specimen (e.g., a wafer or a photomask) to be examined would have to be changed each time a different type of specimen was placed on the chuck (e.g., switching from a wafer to a photomask or from a photomask to a wafer). Manually changing chucks between wafer and photomask inspections is disadvantageous, because additional adjustments (e.g., refocusing the objectives, reattaching vacuum connections, aligning automatic systems, and providing suitable safety features) are usually required when changing chucks. In particular, constantly switching between chucks can damage components of the inspection system (including the chuck itself), reduce the accuracy of specimen analyses, and introduce environmental contaminants into the inspection system. Also, changing out a chuck typically requires particularized knowledge, which operators of a microscopic inspection system may not have. Reducing the adjustments and calibrations that are necessary when switching between a wafer and photomask would reduce damage to the microscopic inspection system, minimize error, and allow for a repeatable, quality controlled microscopic inspection system.
Accordingly, it is desirable to provide a new mechanism for the combined inspection of wafers and photomasks.